The present invention relates to electrically activated acoustic transducers and hydrostatic pressure sensors, and particularly relates to acoustic transducer panels fabricated as a composite of a piezoelectric or electrostrictive ceramic material and a polymeric material as well as methods for fabrication thereof.
The need for detection and control of vibration and noise has long been recognized in technical applications such as hydrophones, actuators, hydrodynamic flow control, hydrodynamic noise control, underwater sound suppression, and structural vibration control. Electromechanical transducers, especially piezoelectric ceramics and polymers, have been used for the interconversion of electrical and mechanical energy in such acoustic applications. Piezoelectric and electrostrictive ceramic/polymer composite materials have been identified as having significant potential for improving the performance of many acoustic transducer systems.
Two of the most important configurations developed for such a composite transducer are those exhibiting the so-called 1-3 and 2-2 connectivity described in detail in U.S. Pat. No. 5,340,510, issued to Leslie J. Bowen, one of the inventors of the present application. (U.S. Pat. No. 5,340,510 is incorporated herein by reference.) The 1-3 composite is a one-dimensionally connected piezoelectric or electrostrictive ceramic phase, e.g., an array of lead zirconate titanate (PZT) rods, pins, or fibers, contained within a three-dimensionally connected polymer phase. The 2-2 composite is made up of two-dimensionally connected ceramic, e.g., parallel PZT strips, separated by two-dimensionally connected parallel polymer strips.
Presently, a thin stiff face plate, e.g., one fabricated from glass-fiber reinforced plastic (GRP) or metal, is bonded to the transducer panel as an end cap or cover plate for the ends of the rods to minimize in-plane motion of the transducer. In some situations, however, the introduction of such a stiffening face plate can lead to other concerns. For example, delamination of the device may occur during use, the device may be susceptible to damage from shock, or the device may not be sufficiently flexible or conformable to, e.g., non-planar mounting surfaces.
Especially desired for the hydrodynamic flow control, hydrodynamic noise control, underwater sound suppression, and structural vibration control applications described above, as well as other applications, has been a flexible, shape-conforming actuator panel configuration which can be applied over and conformed to a large surface area to detect and control vibration and noise over that area. Ideally, such an actuator panel should exhibit a very high actuator authority, provide a uniform surface response, be rugged and shock resistant, and be readily fabricated at relatively low cost. The composite acoustic transducer panels described herein were developed to address that need.